Semi-automatic or automatic stirrup machines or bending machines which work by means of continuous feeding, such as Del Fabro Italian Pat. No. 832,780 are already known in the prior art. Bending and stirrup machines which bend in any shape bars, wire or the like either clockwise or counterclockwise have also been developed.
It has been particularly noticed that a well-known type of machine utilizes a bending method based on two bending pins. The bar that has to be bent is forced to pass through them, so that the bending is carried out either in a clockwise or in a counterclockwise direction, according to the rotation sense of the two fork pins. These pins alternate in order to become hinge elements in coincidence of their axis, thus determining the rotation axes above or under the bar which has to be bent.
A less interesting variant is represented by a machine that utilizes the same fork, but forces it to always rotate on only one of its two axes and therefore makes it pass over or under the bar for its clockwise or anti-clockwise bending.
Another type of machine which has been developed is provided with a fixed fork, around which a bending pin is made to partially rotate clockwise or counterclockwise, making it reenter and pass either above or under the bending bar. The expulsion of the finished product is caused by a pin which is coaxial to the rotation axis of said bending pin. In other cases, this pin acts not only as an expeller, but also as a shearing element. This last type of machine has the severe disadvantage of not being able to carry out a bending which is exactly 180.degree. wide. Such a disadvantage is most likely caused by the fact that the shearing unit and the fixed guiding fork unit have to be necessarily placed near the bending unit.
Moreover, there are other secondary, but equally important disadvantages such that in order to maintain a real bending of 180.degree., it is necessary to turn the guiding unit and the shearing unit away from the bending area. This operation requires a larger amount of bar length and/or wire and the like for the beginning and the end of the stirrup, so causing the well-known defect that the bendings can't be sufficiently precise with respect to the suitable and/or wanted bending radius.